Project description:Oncohistone mutations are crucial drivers for tumorigenesis, but how a living organism responds to and governs the loss-of-function oncohistone remains unclear. Here, we generated a histone H2B triple knockout (3KO) strain in Caenorhabditis elegans, which decreased the embryonic H2B level, disrupted cell divisions, and caused animal sterility. Our genetic screens identified mutations defective in a histone H3-H4 chaperone UNC-85 as suppressors that recovered H2B 3KO fertility. We found that unc-85 mutations reduced chromatin H3-H4 levels and that inhibiting other H3-H4 chaperones or H3-H4 histones also rescued H2B 3KO sterility. The oncohistone H2BE76K mutation disrupts the H2B-H4 interface and causes nucleosome instability, and we showed that blocking H3-H4 chaperones restored cell division defects in C. elegans or human cells carrying H2BE76K. Thus, our results indicate that reducing chromatin H3-H4 rescues H2B loss and suggest that inhibiting H3-H4 chaperones may be a therapeutic strategy to treat cancers resulting from loss-of-function H2B oncohistone.
Project description:A library of unmodified and differentially modified human histones H3 and H4 was prepared using native chemical ligation as described previously (Bartke et al., 2010; Nakamura et al., 2019). The modification status of histone H3 and H4 products was confirmed by LC-MS/MS.
Project description:Histones are essential for chromatin packaging and histone supply must be tightly regulated as excess histones are toxic. To drive the rapid cell cycles of the early embryo, however, excess histones are maternally deposited. Therefore, soluble histones must be buffered by histone chaperones but the chaperone necessary to stabilize soluble H3-H4 pools in the Drosophila embryo has yet to be identified. Here, we show that CG8223, the Drosophila ortholog of NASP, is a H3-H4-specific chaperone in the early embryo. NASP specifically binds to H3-H4 in the early embryo. We demonstrate that, while NASP is non-essential in Drosophila, NASP is maternal effect lethal gene. Embryos laid by NASP mutant mothers have a reduce rate of hatching and show defects in early embryogenesis. Critically, soluble H3-H4 pools are degraded in embryos laid by NASP mutant mothers. Our work identifies NASP as the critical H3-H4 histone chaperone in the Drosophila embryo.
Project description:In eukaryotic cells, inheritable changes in gene expression in response to environmental and developmental stimuli is associated with changes in histone modifications and relies on the passage of these changes into daughter cells during cell division, a process that remains elusive. Here, we show that parental histone (H3-H4)2 tetramers, the primary carrier of epigenetic modifications, are assembled into nucleosomes onto both replicating leading and lagging strands, with a preference for lagging strands of DNA replication forks. This asymmetric distribution of parental (H3-H4)2 is exacerbated in cells lacking Dpb3 and Dpb4, two subunits of DNA polymerase Pol ε. Dpb3-Dpb4 binds (H3-H4)2 and participates in the transfer of parental (H3-H4)2 tetramers onto leading strands of DNA replication forks. Cells lacking Dpb3 and Dpb4 exhibits defects in epigenetic inheritance. These results reveal a previously undocumented mechanism of histone segregation and a direct role for Pol ε in this poorly understood process.
Project description:Mislocalization of CENP-A to non-centromeric regions contributes to chromosomal instability (CIN). Here, we defined a role for the histone H3/H4 chaperone CHAF1B in preventing mislocalization of CENP-A and CIN.
Project description:Signal intensity data for rpd3 delete, H3delta(1-28), H3(K4,9,14,18,23,27Q), H4delta(2-26), H4(K5,8,12,16Q), rpd3 delete H3delta(1-28), and rpd3 delete H4(K5,8,12,16Q) yeast grown in rich (YPD) media
Project description:The goals of this study are to compare Next-Generation-Sequecing (NGS)-derived genome-wide occupancy of H3 and H4 acetylation in S. cerevisiae wildtype and gds1 deletion strain.
Project description:Yeast lacking the H3 or H4 amino termini, and corresponding wild type strains, were grown in synthetic media. These conditions induce Gcn4-activated transcription. Experiment Overall Design: Three replicates of the H4del(2-26) and corresponding wild type strains, and four replicates of the H3del(1-28) and corresponding wild type strains, were performed. Note the strains are congenic, but differ in whether the histones were present on TRP1 marked (H4) or LEU2 marked (H3) plasmids. Samples were analysed using Affymetrix S98 microarrays.
Project description:We have performed a comprehensive analysis of the involvement of histone H3 and H4 residues in the regulation of chronological lifespan in yeast. Residues where substitution resulted in the most pronounced lifespan extension are all on the exposed face of the nucleosome, with the exception of H3E50, which is present on the lateral surface, between two DNA gyres. Other residues that had a more modest effect on lifespan extension were concentrated at the extremities of the H3-H4 dimer, suggesting a role in stabilizing the dimer in its nucleosome frame. Residues implicated in a reduced lifespan were buried in the histone handshake motif, suggesting that these mutations destabilize the octamer structure. All residues exposed on the disk and that caused lifespan extension are known to interact with Sir3. We find that substitution of H4K16 and H4H18 cause Sir3 to redistribute from telomeres and silent mating loci to secondary positions, often enriched for Rap1 or Abf1 binding sites, whereas H3E50 does not. The redistributed Sir3 cause transcriptional repression at most of the new loci, including of genes where null mutants were previously shown to extend chronological lifespan. The transcriptomic profiles of H4K16 and H4H18 mutant strains are very similar, and compatible with a DNA replication stress response. This is distinct from the transcriptomic profile of H3E50, which matches strong induction of oxidative phosphorylation. We propose that different clusters of H3 and H4 residues are involved in either binding to non-histone proteins, or in destabilizing the association of the nucleosome DNA, or disrupting binding of a H3-H4 dimer in the nucleosome, or disturbing the structural stability of the octamer, each category impacting on chronological lifespan through a different path.